A publication of the Advanced Simulation & Computing Division, NA-121.2, NNSA Defense Programs
December 2008
NA-ASC-500-08—Issue 9
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The Power of Interactive Simulation: SC08 Roadrunner Demo
The Los Alamos exhibit booth at SC08 featured a rack of 48 Cell processors of ASC’s Roadrunner hardware to run demonstrations. A demonstration code was run using a new version of the PPM gas dynamics code with a special treatment of the multifluid flow using the Piecewise-Parabolic Boltzmann scheme (PPB). The small interactive runs performed in the demonstrations at SC08 ran to completion in just 7 minutes.
The computational power of the Roadrunner hardware is so great that the flow can be seen to evolve literally as one watches the display screen. The demo showed a real-time display of the computation, not a saved animation! Even on this single rack of Roadrunner hardware, multifluid the PPM code runs fast enough to allow user-driven interaction.
This simple flow problem provides an example of the power of interactive simulation. In the demo, the Roadrunner hardware, together with the very accurate PPM code with PPB multifluid volume fraction advection, enables detailed experiments to be performed while you wait. The PPM code scales linearly up to the full size of the Roadrunner petaFLOPS machine.
Once one has decided on the most interesting parameters for a problem like this one through an exploratory, interactive session, the grid can be increased to hundreds of billions of cells. Phenomenal accuracy and detail can then be achieved for guiding the design, testing, validation, and ultimately, application of subgrid-scale models of such turbulent mixing within larger and much more complex flows.
For more information contact Guy Dimonte, William Dai, or Matt Sheats at LLNL, and Paul Woodward at University of Minnesota, Laboratory for Computational Science and Engineering.
The Roadrunner rack (left) along side the display showing the continuously evolving image and summary information after every 20 time steps in the calculation.
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